Lamp testing device



Filed May 21, 1952 o w S 0a m t o n /t G t v fi m l .6 Dr H V/ b w 4 n U 3 8 I E R E OF m. L H M O m 0 United States Patent LAMP TESTING DEVICE Paul A. Carson, Pittsburgh, Pa., assignor to General Elev tric Company, a corporation of New York Application May 21, 1952, Serial No. 289,040

6 Claims. (Cl. 324-22) This invention relates to an electric lamp testing device particularly useful in testing small size incandescent lamps mounted on a perforated paperboard filler strip or platform.

Many small sizes of incandescent lamps are sold to the customer in packaged lots such that it is laborious to remove and test each lamp individually with the testing equipment which has up till the present been available to lamp dealers as a merchandizing aid. One of the commoner packages is the ten unit package of Christmas tree lamps in a paperboard container comprising a sleeve into which is inserted a filler strip or platform. The center portion of the platform is perforated in two rows of five holes which receive the bases of the lamps. It will be appreciated that the task of removing and replacing the ten lamps from the platform in order to test each one individually is tedious and time consuming.

Accordingly the principal object of the invention is to provide a simple device for rapidly testing a number of incandescent lamps mounted on a paperboard platform without requiring the removal of the lamps from the platform. I

Another object of the invention is to provide a lamp testing device of the above character which will accommodate lamps having difierent sizes of bases.

As is well known, there are two types of Christmas tree lamps in general use, namely the multiple and the series types. In the multiple system, the lamps are connected in parallel across the line and each withstands the full line voltage; in the series system, a group of lamps, for instance eight, are connected in series and each one receives only its proportional share of the line voltage, for instance approximately 15 volts in the case of an eight lamp string. However both types of Christmas tree lamps are generally sold at the same counter, and it will be appreciated that it would be a considerable advantage to the dealer to be able to test both types of lamps by means of a single inexpensive testing device without changeover switches and the attendant possibility of burn-out of a lamp in the case of failure to operate the proper switch.

Accordingly a further object of the invention is to provide a testing device which can be used for testing incandescent lamps differing in voltage and current ratings without requiring the use of changeover switches.

in accordance with the invention, the above described objects are effected by means of a testing device incorporating an insulating block having a generally rectangular passageway or open-top channel formed in its top surface. This channel is proportioned to accommodate the largest base of the types of lamps to be tested, and to permit guiding or sliding the bases of a number of lamps through it while the lamps are mounted in a row on a filler strip or paperboard platform. Extended contact means, at least one of which is of a resilient character, are disposed along the bottom and side Walls of the channel in a manner to engage the end contact and shell of a lamp base guided through the channel, and means are connected across these contacts for applying a 2,746,011 Patented May 15, 1956 regulated voltage to the lamp. In a preferred embodiment of the invention, the means for applying a regulated voltage to the contacts comprise a saturable inductor which is designed to have an output volt-ampere characteristic such as to provide approximately the rated voltage and current to both the common multiple and series types of Christmas tree lamps.

For further objects and advantages and for a better understanding of the invention, attention is now directed to the following description and accompanying drawing. The features of the invention believed to be novel will be more particularly pointed out in the appended claims.

In the drawings:

Fig. 1 is a pictorial view of a testing device embodying the invention and shown in conjunction with a number of miniature incandescent lamps mounted on a paperboard platform or filler strip.

Fig. 2 is a diagram, partly schematic in form, showing the circuit connections of a preferred embodiment of the invention.

Fig. 3 is a graph showing the volt-ampere characteristic of the inductor comprised in the preferred embodiment of the invention.

Fig. 4 .is a diagram partly schematic in form, illustrating another embodiment of the invention.

Referring to Fig. 1, the illustrated embodiment of the invention comprises a generally rectangular box 1, preferably made of sheet metatl and serving as a housing for the current regulating inductor which will be described in greater detail hereinafter. The tester is energized from the usual to volt lighting circuit through the line core and plug 2. On the top face of the box is fastened an insulating block 3, shown partly cut away for greater clarity, and which is preferably made of a dense heat resisting plastic material. A generally rectangular channel or slot 4 extends through the longer dimension of the block and is defined by the side walls 5 and 6 and the bottom surface 7. The upper opening or throat of the channel is defined by the edges of the top plates 8 and 9 fastened on the block. The throat is preferably just wide enough to accommodate the largest base of the different lamp types to be tested; this feature is desirable as a safety measure in order to prevent the operator from accidentally entering a finger into the slot with the resultant electric shock hazard.

Near the center of the slot on its bottom surface 7, is fastened a contact strip 11, preferably bowed slightly upwardly and extending some distance in the direction of the slot on both sides of its center. This contact strip is adapted to engage the bottom or end contact of a lamp when it is guided through the channel. Top plate 8 has a shallow recess along its underside which forms, in conjunction with the upper surface of insulating block 3, a relatively narrow groove 12 which abuts laterally from side wall 5, into the channel. Into this groove is fitted a resilient contact member 13 which may take the form of a curved spring wire normally projecting laterally into the channel 4 and partially obstructing it. As illustrated, the spring wire member 13 bears some resemblance to a safety pin having a full loop at 14 where it is pivotally fastened within the groove 12, and having one end fixed at 15 where it passes down through the block. Thus, when a lamp is guided through the channel 4, the shell of its base engages the sprung leg portion 13 of spring 13 which curves into the channel, thereby making electrical contact with it, and the spring is forced back into the groove to the extent necessary to permit the lamp to pass through. It will be readily appreciated that the arrangement is capable of accommodating more than one size of base, the spring being merely pushed back into the groove to a greater or lesser extent depending upon the size of the base. A similar spring member maybe mounted in the opposite side wall 6 of the channel,

although such is not strictly necessary and a straight length of wire 16 permanently fixed to that side wall, as illustrated in the drawing, has been found adequate for the purpose.

' A number of lamps18 mounted in a row on a paperboard filler strip or'platform 19 have been illustrated in operative position with respect to the channel of the tester." The operator grasps the platform with one hand, at the same time holding any of the lamps that should happen to be loose in the strip, and guides it forward so that the bases of the lamps enter the channel. As

each lamp in' turn approaches the center of the channel,

it is engaged by the contact members within it and lights up, a defective one of course being indicated by the failure to light. It-will be appreciated that, by reason of the flexible nature of the contacts, various sizes of bases may be accommodated and Christmas tree lamps of the multiple outdoor type having a larger base than that of the multiple indoor type illustrated at 18 may also be tested. A single lamp 20 of the series Christmas tree type has also been illustrated, and it may likewise be tested, either singly or mounted on a platform along With a number of others, by guiding it through the channel of the tester.

Referring to Fig. 2, the test circuit comprises the con ductors 21, 22 which are adapted to be connected at 23 to the usual 115-120 volt, 60 cycle lighting circuit.

One of the conductors, 21 in the drawing, is connected to the bottom contact strip 11. The other conductor 22 leads to the series inductor 24 and thence to the lateral or side contacts,,namely spring 13 and wire 16 which are connected in common.

The series inductor 24 comprises a winding 25 (shown Lin section) on a laminated soft iron core 26. Thermal- ,ber of turns and the cross section of the core are'propor- 'tioned to achieve an output volt-ampere characteristic such as to furnish the proper voltage and current to at least two lamps having widely different voltage and current ratings. For instance referring to Fig. 3, there is illustrated 'a negative volt-ampere characteristic curve 27 which has been found suitable for testing the three common ratings of Christmas tree lamps, namely the outdoorfmultiple having a rating of 10 watts at 118 volts, the indoor multiple having a rating of 7% watts at 118 volts, and the indoor series having a rating of 4.65 watts at 15 volts. The nominal or rated voltage-current operating points of these various lamps have been indicated by the circled dots ON, IM and 18 for the three types of lamps in the order named. It will be observed that t the volt-ampere characteristic of the inductor passes close to the voltage current points of all three types of lamps; it will be appreciated that exact coincidence is not necessary for testing purposes and that some deviation, particularly on the under-voltage side, may readily be tolerated.

As an example of an inductor suitable for the present purpose and providing the output volt-ampere characteristic illustrated, the winding 25 of Fig. 2 may consist of 1550 turns of .0126 inch diameter wire wound on the central leg 28 of core 26. The core may be a /2 inch thick stack of butted E-shaped punchings, resulting in a core of overall dimensions 2% inch by 1 /8 inch, the central leg being 1 /8 inch by /8 inch wide, and

the two windows being 1% inch long by 56 inch wide;

vreadily be adjusted to include substantially the operating voltage-current points of the selected lamp types, as illustrated in Fig. 3.

Referring to Fig. 4, there is shown an alternative circuit wherein the inductor 24 previously described in connection with the embodiment of Fig. 2, is replaced by an incandescent lamp 30. ,This lamp has a positive temperature characteristic such that its resistance increases with the current passing through it. For instance, for the application considered, it has been found that volt tungsten incandescent lamps having nominal ratings of 25, 30 or 40 watts may be used for regulating the current in testing the types of Christmas tree lamps mentionedabove. The volt-ampere characteristic of the 40 watt lamp under static conditions, that is, at thermal equilibrium for anyone current value, is reasonably close to that of the saturable inductor 24 considered earlier. However by reason of the thermal inertia of the filament, there is a certain time lag in achieving the required position on the static volt-ampere characteristic, and since the thermal inertia of the small Christmas tree lamp is less than that of the regulating lamp, occasionally the Christmas tree lamp being tested would burn out. Accordingly, it has been found preferable to use an incandescent lamp of a smaller rating than the optimum, even though the lamp being tested may not light up to full brilliance. For instance, a 115 volt lamp of 25 watt rating has been found generally preferable to the 40 watt lamp, and a testing device incorporating this lamp as a series current regulator will safely test all three sizes and types of Christmas tree lamps mentioned above.

While certain specific embodiments of the invention have been shown and described, it will of course be appreciated that various modifications may be made in the details thereof without departing from the invention. The appended claims are therefore intended to cover any such modifications coming within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A tester for platformed lamps comprising a body structure defining an open-top channel through which such lamps may be passed and tested in rapid succession, a single pair of contact means within said channel to engage lamps having bases of different sizes, and means connected to said pair of contact means for supplying thereto a regulated voltage, the volt-ampere characteristic of said means including substantially the voltagecurrent operating points of selected groups of lamps of different voltage ratings.

2. A tester for platformed lamps comprising a body structure defining an open-top channel through which such lamps may be passed and tested in rapid succession, a single pair of contact means within said channel to engage lamps having bases of dilferent sizes, and means connected to said pair of contact means for supplying a regulated voltage thereto and comprising means having a negative-volt-ampere characteristic for automatically supplying to selected I groups of lamps of widely different voltage ratings the voltages required for satisfactory testing at rated values.

3. A tester for electric lamps comprising an insulating block having a bottom surface and lateral'walls defining a straight channel, a first contact means comprising an extended strip disposed along said bottom surface lengthwise of said channel, a second contact means comprising a resilient spring member mounted on one of said lateral walls and disposed to obstruct partially said channel and to be forced aside when engaged by the base shell of a lamp guided through said channel, and means connected across said contact means for applying a regulated voltage thereto and having an output volt-ampere characteristic coinciding substantially with the voltage-current operating points of at least two lamps of different voltage ratings to be tested thereby.

4. A tester for platformed lamps comprising an insulating block having a bottom surface and lateral walls A defining a straight channel, a first contact means comprising an extended strip disposed along said bottom surface lengthwise of said channel, a second contact means comprising a resilient member mounted on one of said lateral walls and disposed to obstruct partially said channel and to be forced aside when engaged by the base shell of a lamp guided through said channel, and means connected across said contact means for applying a regulated voltage thereto and comprising a saturable inductor having an output volt-ampere characteristic coinciding substantially with the voltage-current operating points of selected groups of lamps of difierent voltage ratings to be tested thereby.

5. A tester for platformed electric lamps comprising an insulating block having a bottom surface and lateral walls defining a straight channel of a size proportioned to accommodate bases of lamps guided therethrough and having a constricted upper throat opening preventing the insertion of a human finger therein, a first contact means comprising an extended strip disposed along said bottom surface lengthwise of said channel for contacting the end contact of a lamp, a resilient spring wire member of general safety pin configuration, a narrow groove in one of said lateral walls, said spring member being pivotally fastened in said groove with a sprung portion curving laterally into said channel so as to engage the base shell of a lamp guided through said channel and to be forced aside thereby, and means connected across said contact means for applying a regulated voltage thereto and comprising a saturable inductor having an output volt-ampere characteristic coinciding substantially with'the voltagecurrent operating points of selected groups of lamps of different voltage ratings to be tested thereby.

6. A tester for platformed lamps comprising an insulating block having a bottom surface and lateral walls defining a straight channel, a first contact means comprising an extended strip disposed along said bottom surface lengthwise of said channel, a second contact means comprising a resilient member mounted on one of said lateral walls and disposed to obstruct partially said channel and to be forced aside when engaged by the base shell of a lamp guided through said channel, and means connected across said contact means for applying a regulated voltage thereto and comprising an incandescent lamp having a positive temperature resistance characteristic and a rating such as to provide voltage-current values substantially corresponding to those of two groups of lamps having different voltage and current ratings.

References Cited in the file of this patent UNITED STATES PATENTS 1,367,285 Stimmel Feb. 1, 1921 1,912,424 Batter June 6, 1933 2,478,999 Briseno Aug. 16, 1949 

